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The T2K Experiment - Where is the anti-matter?

A million pound detector has been built at the University of Warwick as part of a vital experiment to investigate fundamental particles - neutrinos. The experiment aims to measure neutrinos at the start of their journey and then again at the end 300 kilometres away to see how they've changed. Understanding neutrinos will tell us more about the physics of the universe and help explain why the universe is made of matter rather than anti-matter.

Associate Professor, Dr Gary Barker said, "It's thought that in the Big Bang that created the universe, matter and anti-matter were created in equal amounts, but it's clear that everything we observe today is only consisting of matter, so the question is where has the anti-matter gone?"

50 trillion neutrinos from the sun pass through us every single second, but as we do not notice these they are hard for scientists to detect. The T2K experiment generates its own beam of neutrinos rather than relying on studying those from the sun.

The detector built at Warwick as been installed in J-PARC on Japan's east coast. Here, scientists accelerate protons into a target and use them to produce a beam of neutrinos. They fire a beam of muon-neutrinos through the Warwick detector aiming at a second detector 300km away at another laboratory called Super-KAMIOKANDE at Kamioka and measure its behaviour. The experiment hopes to investigate the phenomenon of "neutrino oscillations" by looking for "muon neutrinos" oscillating into "electron neutrinos".

Work at Warwick

There are 62 institutes across 12 different countries contributing to the T2K experiment. Within this broad collaboration Warwick has made some important and significant contributions towards construction, quality assurance, calibration hardware and software analysis.

Warwick's construction responsibilities include the testing of photosensors and optical fibres for the entire ND280 detector and construction of all 6 modules of the P0D ECal. Warwick are also important contributors throughout the software framework including the calibration, tracking and particle ID packages.

T2K Schematic

On the Eastern coast of Japan, the national accelerator complex J-PARC accelerates a 30GeV proton beam onto a graphite target, generating mesons which decay to produce a beam of muon neutrinos. 280m downstream lies the near-detector ND280. Its task is to measure the initial beam flux and to make critical measurements of neutrino interaction cross-sections.

The T2K far detector is located 295km west of J-PARC near Kamioka: Super-Kamiokande is a 50kton water-Cherenkov detector which will measure the muon and electron neutrino fluxes after oscillation. Both detectors are situated 2.5° off the beam-axis to give a sharper energy spectrum than conventional on-axis beams.

T2K Physics Goals

The primary goal of T2K is a measurement of θ13 through a νe appearance analysis, in addition to improving current values for Δm223 and θ23 from νμ disappearance. In doing this, T2K will also make an important contribution to current world knowledge of neutrino-nucleon cross-sections.